Stephen Hawking’s Great Question –“Why Isn’t the Milky Way Crawling With Mechanical or Biological Life?”



“If the argument about the time scale for the appearance of life on Earth is correct”, Stephen Hawking observed, echoing Enrico Fermi’s infamous question–Where is Everybody– “there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self-designing mechanical or biological life forms?”

In his famous lecture on “Life in the Universe”, Stephen Hawking, who was laid to rest in 2018 in Scientists’ Corner at Westminster Abbey, between Isaac Newton and Charles Darwin, asked: “What are the chances that we will encounter some alien form of life, as we explore the galaxy?”

Why hasn’t the Earth been visited?

Why hasn’t the Earth been visited, and even colonized? Hawking asks, “I discount suggestions that UFO’s contain beings from outer space. I think any visits by aliens, would be much more obvious, and probably also, much more unpleasant.”

The Aliens Before Us –“We are Not the First Technological Civilization” (Or, are We?)


“What is the explanation of why we have not been visited?” asks Hawking. “One possibility is that the argument, about the appearance of life on Earth, is wrong. Maybe the probability of life spontaneously appearing is so low, that Earth is the only planet in the galaxy, or in the observable universe, in which it happened. Another possibility is that there was a reasonable probability of forming self reproducing systems, like cells, but that most of these forms of life did not evolve intelligence.”

Hawking’s Question Foreshadows New Research on Alien Life

“What really surprised me about the results is that we may realistically find signs of life on other planets in the next 5 to 10 years,” said Caprice Phillips, at the Ohio State University who led a team that modelled how the new James Webb Space Telescope, scheduled for liftoff October 31, 2021, instruments would respond to varying clouds and atmospheric conditions, then produced a ranked list of where the telescope should search for life.

“Humankind has contemplated the questions, ‘Are we alone? What is life? Is life elsewhere similar to us?'” said Phillips. “My research suggests that for the first time, we have the scientific knowledge and technological capabilities to realistically begin to find the answers to these questions,” she added.

“I think we’re going to have strong indications of life beyond Earth within a decade, and I think we’re going to have definitive evidence within 20 to 30 years,” NASA’s then  chief scientist Ellen Stofan said in 2015 during a panel discussion that focused on the space agency’s efforts to search for habitable worlds and alien life.

“We know where to look. We know how to look,” Stofan added. “In most cases we have the technology, and we’re on a path to implementing it. And so I think we’re definitely on the road.”

“Proof of Alien Life in 20 Years” –NASA



Intelligence may not have long-term survival value

We are used to thinking of intelligent life, as an inevitable consequence of evolution, Hawking emphasized,  but it is more likely that evolution is a random process, with intelligence as only one of a large number of possible outcomes. Intelligence, Hawking believes contrary to our human-centric existence, may not have any long-term survival value.

In comparison, the microbial world will live on, even if all other life on Earth is wiped out by our actions. Hawking’s main insight is that intelligence was an unlikely development for life on Earth, from the chronology of evolution:  “It took a very long time, two and a half billion years, to go from single cells to multi-cell beings, which are a necessary precursor to intelligence. This is a good fraction of the total time available, before the Sun blows up. So it would be consistent with the hypothesis, that the probability for life to develop intelligence, is low. In this case, we might expect to find many other life forms in the galaxy, but we are unlikely to find intelligent life.”

Odds it can Evolve to build and operate radio telescopes?

Once there is life of any kind suggests astrobiologist Charles Lineweaver “what is the probability that it will evolve into a human-like intelligence that can build and operate radio telescopes? We define intelligence this way not out of some geeky technophilic perversity but because posed this way, we have the ability to answer the question by searching for other telescopes with our telescopes. So far, no signals from intelligent aliens have been identified.”

“The Radio Species” –Scientists Doubt ‘Human Niche’ Would Be Filled If We Go Extinct

Another possibility is that there is a reasonable probability for life to form, and to evolve to intelligent beings, but at some point in their technological  development “the system becomes unstable, and the intelligent life destroys itself. This would be a very pessimistic conclusion. I very much hope it isn’t true,” concludes Hawking.

The image at the top of the page depicts a view of the night sky from a hypothetical planet within the youthful Milky Way galaxy 10 billion years ago. The heavens are ablaze with a firestorm of star birth. Glowing pink clouds of hydrogen gas harbor countless newborn stars, and the bluish-white hue of young star clusters litter the landscape. The star-birth rate is 30 times higher than it is in the Milky Way today. Our Sun, however, is not among these fledgling stars. The Sun will not be born for another 5 billion years. (Credit: NASA, ESA and Z. Levay / STScI.)

Maxwell Moe, astrophysicist, NASA Einstein Fellow, University of Arizona via Life in the Universe and American Physical Society







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